This is the E-Flite 4100Kv Park 370 Brushless Motor.  This motor is great if you want to get better and more efficient performance for sport and aerobatic park flyers.

Features:

• Slotless 2-pole design
• Prop adapter and gold-plated connectors included
• Excellent Motor for small airplanes between 10 oz â“ 14 oz (280 g â“ 400 g)
• Great upgrades for Speed 280 and Speed 370 applications
• Adapter plate for mounting to GWS- and E-flite-style gearboxes and prop adapter included
• Available with a 10T and 12T pinion gear for easy upgrade for 6.6:1 or 5.33:1 gearbox

Specifications:
Type: Brushless
Size: Park 370
Bearings or Bushings: Bearings
Recommended Prop Range: 9x6 to 12x6
RPM/Volt (Kv): 4100
Resistance (Ri): .1 ohms
Idle Current (Io): 1A @10V
Shaft Diameter: 2mm (.08 in)
Weight: 48 g (1.7 oz)
Diameter: 20 mm (.8 in)
Length: 30 mm (1.2 in)
Continuous Current: 8A
Maximum Burst Current: 13A
Cells: 6-10 NiCd/NiMh or 2-3 LiPo
Speed Control: 10 - 25 Amp Brushless